Various materials used in building construction and other civil engineering projects such as roads and bridges are susceptible to water penetration resulting either from their inherent properties or imperfections such as cracks or pores. Reducing or eliminating water penetration through structures formed of these materials often is desirable such as for below-grade building walls, and may be critical in certain structures, such as those which house expensive electrical equipment, or tunnels which permit passage of vehicular or pedestrian traffic under bodies of water.
In conventional waterproofing applications, the waterproofing material is "post applied" to an existing concrete structure. In other words, a water-proofing agent is coated or laminated onto pre-formed structures; the waterproofing agent is then applied after the concrete is shaped and cured. Available conventional waterproofing agents include ethylene propylene diene monomer (EPDM) sheets, polyvinyl chloride sheets, neoprene sheets, bentonite panels, built-up asphalt systems, coal tar-based, and other asphalt-based compositions. Asphalt-based compositions are currently preferred; most preferred are preformed, flexible sheet-like waterproofing laminates of a support film(s) and a bituminous layer(s) such as described in U.S. Pat. Nos. 3,741,856; 3,853,682; and 3,900,102. Bituthene.RTM. brand of waterproofing is an example of a popular commercial membrane.
In many inner-city construction projects, the concrete foundation of one structure is poured very close to the foundation and/or property line of its neighbors. In these situations, a permanent concrete form, typically constructed using wooden planks, is assembled along the exterior of the foundation. This is referred to as "vertical lagging" or simply "lagging". During a lagging operation, it is virtually impossible to apply a conventional post applied waterproofing membrane to the cured exterior of the foundation because the exterior surface of the concrete is facing against the lagging form and thus cannot be exposed or rendered accessible for application of a waterproofing membrane.
Accordingly, attempts have been made to affix a pre-applied waterproofing membrane to the lagging form before the wet concrete is poured. Pre-applied waterproofing systems have been limited to bentonite based products including Volclay Panels, Paraseal, and Claymax. These products rely on the ability of the bentonite clay to expand on contact with water and create an impermeable layer to water migration. However, the rigidity of the lagging material/structure actually prevents the formation of an expanded wet clay layer of a desirable density high enough to qualify the material as impermeable. Of primary concern is the unevenness and the voids in the lagging substrate which may prevent the formation of the impermeable clay layer.
Conventionally preferred asphaltic based waterproofing membrane systems have several significant deficiencies when applied with the adhesive facing out in a lagging situation. First, they tend to oxidize during short periods of outdoor exposure and "mud cracks" develop on the adhesive surface. The oxidized surface does not bond to the post cast concrete (i.e. concrete that is subsequently cast). Second, the exposed adhesive surface of the waterproofing membrane tends to become fouled by the elements and by dust. Accordingly, it would be desirable to have an essentially non-tacky waterproofing membrane which can be pre-applied to a concrete form, resist chemical and physical changes from real time outdoor exposure, and develop a strong, fully-adhered bond to the post cast concrete structure (ie. the concrete structure which is formed subsequently to the application or installation of the waterproofing membrane).
An objective of the present invention is to provide a waterproofing membrane which can be pre-applied to a concrete form and which can adhere strongly to the post cast concrete.
It is also an objective to provide a waterproofing membrane to resist chemical and physical changes during outside exposure and still have the capability for forming a strong and intimate bond to post-cast concrete.
It is further an objective to provide a highly weatherable waterproofing membrane which is essentially not tacky to the touch.
Also, it is an objective to provide a method for pre-applying waterproofing membranes which become fully adhered to the resulting post cast concrete structure.
It is yet another objective to provide a novel waterproofing post cast concrete structure.